Quarterly Data (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share Basic [Abstract]
Average common shares outstanding - basic	853,000,000	663,000,000	779,000,000	663,000,000
Earnings Per Share, Basic	$ 0.34	$ 0.93	$ 0.62	$ 1.94
Earnings Per Share Diluted
Average common shares outstanding - diluted	856,000,000	664,000,000	781,000,000	664,000,000
Earnings Per Share, Diluted	$ 0.33	$ 0.93	$ 0.62	$ 1.94
Selected Quarterly Financial Information [Line Items]
Revenues	$ 5,954,000,000	$ 4,496,000,000	$ 10,640,000,000	$ 9,451,000,000
Operating Income (Loss)	714,000,000	1,034,000,000	1,073,000,000	2,236,000,000
Net Income Loss	289,000,000	621,000,000	490,000,000	1,290,000,000
Exelon Generation Co L L C [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	3,753,000,000	2,455,000,000	6,492,000,000	5,098,000,000
Operating Income (Loss)	384,000,000	647,000,000	656,000,000	1,448,000,000
Net Income Loss	165,000,000	443,000,000	332,000,000	938,000,000
Commonwealth Edison Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	1,281,000,000	1,444,000,000	2,670,000,000	2,910,000,000
Operating Income (Loss)	142,000,000	254,000,000	368,000,000	454,000,000
Net Income Loss	42,000,000	114,000,000	129,000,000	183,000,000
PECO Energy Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	715,000,000	842,000,000	1,590,000,000	1,996,000,000
Operating Income (Loss)	151,000,000	161,000,000	327,000,000	372,000,000
Net Income Loss	80,000,000	83,000,000	177,000,000	210,000,000
Baltimore Gas and Electric Company [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	616,000,000	674,000,000	1,312,000,000	1,650,000,000
Operating Income (Loss)	52,000,000	54,000,000	41,000,000	208,000,000
Net Income Loss	$ 16,000,000	$ 16,000,000	$ (14,000,000)	$ 97,000,000